Carpets and other fabrics made from synthetic yarns are currently colored using two well-established processes. The first process involves converting colorless white yarns into carpet, and dyeing the carpet in a dye bath. This process is referred to as the “acid dye process.” The acid dye process can be either a batch or a continuous dyeing operation. Each dyeing operation requires a large volume of water, steam to set the dyes, and heat to dry the carpet. In addition, collection and disposal of excess dye and acidified performance enhancing solutions add manufacturing cost and place additional burden on waste management and water treatment facilities. The second process adds color pigments into the polymer during the melt spinning process. This process is referred to as the “solution dye process.” The solution dye process is a low cost operation, but in comparison to the acid dye process it imposes undesirable inventory allocation measures on the fiber producer and the carpet mill. In order to meet consumer demand, then, the fiber producer and carpet mill may need to keep a costly inventory of colored yarns produced by the solution dye process. Variable production demands and large inventory costs can affect inventory flexibility with the result being the color availability of solution dyed carpets is undesirably limited.
Carpets and other fabrics are currently treated with topical chemistries for improved stain resistance and/or soil resistance. For nylon carpets, both stain blocker (e.g. acid dye blocker) and anti-soil with fluorochemicals are traditionally used. For polyester carpets, such as polyethylene terephthalate (2GT) and polytrimethylene terephthalate (3GT) carpets, and polypropylene carpets, anti-soil chemistry may be applied topically to the tufted carpet as part of the carpet finishing process. Polyester and polypropylene carpets typically do not require a stain blocker treatment because of inherent stain resistance to acid dyes and stains owing to their lack of amine end groups that function as acid dye sites.
Topical application at the carpet mill can be in the form of exhaust application and spray application. Exhaust application (i.e. flex-nip process at high (300-400 wt. %) wet pick-up), is known to provide an improvement in efficacy over spray-on applications at 10-20 wt. % wet pick-up of anti-soil. Exhaust applications typically use higher amounts of water and energy to dry and cure the carpet than do spray applications. Spray-on fluorochemical products are designed to use less water and energy than exhaust applications, but do not impart satisfactory anti-soil properties.
While various processes are in use in the carpet industry for the dyeing and finishing of carpets, some large scale and some small, most of the carpet made today is dyed and finished on a continuous dye range. This is done mainly in one of two ways: In one case, a two stage process is employed, where the carpet is steamed and dyed first, steamed, rinsed, and excess water extracted; then stain blocker (SB) is applied, the carpet is again steamed and washed, and then anti-soil fluorochemical (FC) is applied in the form of a foam or liquid spray and the carpet is finally dried. (See e.g. U.S. Pat. Nos. 5,853,814; 5,948,480 and WO2000/000691). In the second, somewhat improved case, called the co-application process, the carpet is also steamed and dyed first, steamed again, rinsed and extracted; and then a blend of SB and FC is applied together at high wet pick up, after which the carpet and chemicals are exposed once again to steam to fix the treatment, followed by drying. (See e.g. U.S. Pat. Nos. 6,197,378 and 5,520,962). In both cases, low pH solutions, excess water, and energy are required for the SB and FC to penetrate the carpet and achieve uniform coverage. In sum, the typical process is as follows: BCF yarn→Twist→heat set→tufting→carpet→dye→stain block/anti-soil.